The present disclosure relates an inverter device that includes an inverter circuit that converts power between DC power and multi-phase AC power.
Switching elements that constitute an inverter circuit that converts power between DC power and AC power are often provided with a drive signal from a control device via a drive circuit. The switching elements are controlled so as to perform turn-on, in which the switching elements are brought from an off state into an on state, and turn-off, in which the switching elements are brought from the on state into the off state, on the basis of the drive signal. In the case where a current that exceeds a reference flows through the switching elements in the on state (in the case of an overcurrent state), the switching elements are controlled to the off state by the control device or the drive circuit. For example, Japanese Patent Application Publication No. 2012-151592 identified below describes a feature wherein a gate voltage of IGBTs (insulated gate bipolar transistors) is turned off (0 V) in the case where an overcurrent flows because of a short circuit or the like (see paragraphs [0027], [0030], [0032], etc.).
When the switching elements are abruptly turned off with a large current flowing therethrough, however, a significantly high surge voltage may be generated to significantly damage the switching elements. Therefore, soft turn-off (soft switching) in which the transition time of the turn-off is extended by making variations in drive signal slow is occasionally performed. In the soft turn-off, however, a current that flows through the switching elements is decreased at a reduced speed since the transition time is extended. Therefore, the switching elements tend to consume large energy (loss, heat) compared to the normal turn-off.